Refractory products used in a high-temperature furnace are brought into contact with a molten slag and a molten metal and subjected to various damages. In particular, lining bricks located in a slag line of a vessel can be corroded significantly by molten slag (slag attack) within a short period of time. In addition, the bricks spall after the repetition of a heating/cooling cycle. Graphite-containing refractory products such as magnesia-carbon (MgO-C) brick and a castable containing metal fibers having an improved spalling resistance have been recently put into practical use.
Conventional refractory products improve the slag attack resistance by adding carbon (graphite) in the refractory product or increasing the density of the refractory product, thereby suppressing penetration of the molten slag into the refractory product.
Japanese Patent Registration No. 1401778 discloses a product formed by adding a metal such as aluminum in a carbon-containing refractory product so that the metal, aluminum in the refractory product is preferentially oxidized to prevent high-temperature oxidation of carbon.
Published Unexamined Japanese Patent Application No. 57-500788 discloses a composite body formed by adding a powdered metal to an oxide-based ceramic in order to improve abrasion resistance and toughness of the oxide-based ceramic.
Published Unexamined Japanese Patent Application No. 49-99512 discloses a method of impregnating a metal in a sintered ceramic matrix.
The above conventional refractory products, however, have the following problems in terms of improvements in high-temperature characteristics.
1 When the density of a refractory brick is increased, the spalling resistance is generally decreased. Therefore, the brick easily cracks due to a thermal stress.
2 A carbon-containing refractory product is significantly damaged at high temperature because the oxide and the contained carbon in the product directly react. Even at low temperature, since the graphite easily oxides, depending on its use atmosphere and temperature are limited.
3 In a carbon-containing refractory product containing carbon and metal aluminum, the contained metal is oxidized within a short time period. Therefore, since oxidation of carbon cannot be sufficiently suppressed, a reduction in slag attack resistance occurs in an initial stage. In this case, the slag attack resistance means a resistance against damage caused by a molten slag which penetrates into the refractory product along open pores and dissolves the refractory product.
Use in a furnace is not contemplated for a conventional metal-impregnated ceramic product. An impregnated metal of the ceramic body flows out at a temperature higher than the melting point of the metal or the ceramic body consists of a composition having a low slag attack resistance, the ceramic body is therefore unsuitable for use in a high-temperature furnace. There are open pores and closed pores in refractory product.
Generally, properties (e.g., slag attack resistance and a spalling resistance) of refractory brick are largely affected by, e.g., amounts, shapes, sizes, and distributions of pores and voids. That is, when the porosity is increased, the brick becomes vulnerable to penetration of a molten slag. To the contrary, when a total amount of pores and voids is decreased to increase the density of a brick, spalling resistance is reduced. Therefore, to improve both the slag attack and Spalling resistances in conventional bricks, an amount of pores must be decreased while that of voids is increased. However, it is generally difficult to manufacture such a refractory product.
The present invention has been made in consideration of the above situation, and has as its object to provide a metal-impregnated refractory product excellent in various high-temperature characteristics, particularly, a slag attack resistance and a gas attack resistance and having a long life, and a method of manufacturing the same.